1. Field of the Invention
The present invention relates to a spread illuminating apparatus used as an illuminating means for a liquid crystal display, and more particularly to a frame of such a spread illuminating apparatus.
2. Description of the Related Art
A liquid crystal display (hereinafter referred to as xe2x80x9cLCDxe2x80x9d) featuring low profile, small occupied volume and light-weight has been extensively used in various electric products such as cellular phones and personal computers, and the demand therefor has been increasing. Since a liquid crystal used for the LCD does not emit light by itself, the LCD requires a separate illuminating means when used in dark places where sunlight or room light is not satisfactorily available. The illuminating means is demanded to be small in size and low in power consumption, and recently a spread illuminating apparatus of side light type (light conductive plate type) is often used as the illuminating means.
FIG. 5 shows an exploded perspective view showing an embodiment of a conventional spread illuminating apparatus of side light type having a frame (housing).
As shown in the figure, a spread illuminating apparatus 1xe2x80x2 generally comprises a light conductive plate 2 made of a light-transmissible material, lamps 5a and 5b comprising respective light conductive bars 3a and 3b and respective spot-like light sources 4a and 4b and disposed respectively along side surfaces 8 and 18 of the light conductive plate 2, an FPC (flexible printed circuit) 6 having the light sources 4a and 4b mounted thereon, light reflection members (reflectors) 13a and 13b covering the lamps 5a and 5b, respectively, and frames 7a and 7b covering the peripheral portion of the spread illuminating apparatus 1xe2x80x2 comprising the above-mentioned members. Lights emitted from the lamps 5a and 5b enter the light conductive plate 2 and are reflected therein so as to irradiate an LCD L disposed under the light conductive plate 2.
A light reflection pattern 29 is formed on a top surface (observation surface) 25 of the light conductive plate 2 so that the lights having entered the side surfaces 8 and 18 (hereinafter referred to also as xe2x80x9cincidence surfacesxe2x80x9d) are reflected therein and emitted through a bottom surface 26 in a uniform spread manner in the direction of the LCD L. The light reflection pattern 29 comprises a plurality of grooves 27 and a plurality of flat portions 28 adjacent thereto, and is oriented parallel to the longitudinal direction of the light conductive bars 3a and 3b. The light reflection pattern 29 may comprise only grooves continuously formed. The grooves may be oriented so as to have a predetermined angle with respect to the longitudinal direction of the light conductive bars. With the light reflection pattern thus configured, the lights having entered the light conductive plate 2 are reflected in a substantially uniform manner at the entire top surface of the light conductive plate 2, and irradiates the LCD L disposed under the light conductive plate 2.
The lamps 5a and 5b comprise the respective light conductive bars 3a and 3b and the respective light sources (for example, light emitting diodes) 4a and 4b. Optical path conversion means 12a and 12b are formed on respective one side surfaces of the light conductive bars 3a and 3b, and the light sources 4a and 4b are disposed close to respective one ends of the light conductive bars 3a and 3b. The light sources 4a and 4b are mounted on the FPC 6 and fixed thereto by soldering. The light reflection members 13a and 13b are disposed so as to cover respectively the light conductive bars 3a and 3b and two opposing sides of the light conductive plate 2 when the spread illuminating apparatus 1xe2x80x2 is assembled.
The light reflection members 13a and 13b are provided in order to efficiently guide the lights emitted from the light sources 4a and 4b into the light conductive plate 2, to prevent the light conductive bars 3a and 3b from getting damaged due to a contact with other members, or to enhance a dust-proof effect for the light conductive bars 3a and 3b. The light reflection members 13a and 13b are shaped substantially like U-letter in section, and cover the longitudinal surfaces of the light conductive bars 3a and 3b except a surface facing the light conductive plate 2. The reflection members 13a and 13b are structured such that a film evaporated with a metal such as silver, or a white film is attached to a hard resin member or that a metal plate such as an aluminum plate or a stainless steel-plate is bent.
The frames 7a and 7b are each structured such that a metal plate is bent substantially like U-letter, are shaped so as to constitute respective halves of a picture frame with portions corresponding to an observation surface cut away when the spread illuminating apparatus 1xe2x80x2 is assembled, and cover the lamps 5a and 5b and a peripheral portion of the light conductive plate 2. Thanks to the frames 7a and 7b, the components of the spread illuminating apparatus can be reliably fixed. And, since the light sources can be fixed in a predetermined position with respect to the respective light conductive bars, the lights emitted from the light sources can be efficiently guided in the light conductive bars.
However, the spread illuminating apparatus with the above-described frames has the following problems.
Since an area of the spread illuminating apparatus 1xe2x80x2 with the frames 7a and 7b mounted thereon is substantially equal to an area of the LCD L, and also, since the spread illuminating apparatus 1xe2x80x2 is superimposed over a top surface of the LCD L, the apparatus, as a whole, has a thickness equal to a total thickness of the LCD L, the lamp 5a or 5b (also the light reflection member 13a or 13b if attached), and the frame 7a or 7b. As a result, the total thickness is considerably increased.
Further, since lower frame portions of the frames 7a and 7b are inserted between the light conductive plate 2 and the LCD L, a wasted space is given for their thickness between the light conductive plate 2 and the LCD L.
FIGS. 6 to 8 are detailed schematic representations of the total thickness of the apparatus, and the space given between the light conductive plate 2 and the LCD L when the spread illuminating apparatus 1xe2x80x2 is superimposed over the top surface of the LCD L.
FIG. 6 is an exploded perspective view of the entire apparatus substantially comprising the LCD L, the frame 7 disposed on the top surface of the LCD, and the light conductive plate 2 and the lamp 5 enclosed in the frame 7.
FIG. 7 is a cross-sectional view through the line Exe2x80x94E in FIG. 6, and FIG. 8 is a cross-sectional view through the line Fxe2x80x94F in FIG. 6.
The light conductive plate 2 and the lamp 5 are disposed so as to be enclosed in the frame 7. In other words, the frame 7 covers the peripheral portion of the light conductive plate 2, and the lamp 5. Thus, the entire apparatus has a thickness equal to a total of the thickness P3 of the LCD L and the thickness P2 of the entire frame 7. A lower portion of the frame 7 is disposed between the light conductive plate 2 and the LCD L, and a space equivalent to the thickness P1 of the lower portion of the frame 7 is generated. Even when the P1 is very slight, a screen of the LCD looks retracted as viewed from above the light conductive plate 2, which gives a sense of discomfort to an observing person. In order to eliminate this trouble, the P1 of the lower portion of the frame 7 may be reduced. However, this sacrifices the strength of the frame.
The present invention has been made in the light of the above problems. It is an object of the present invention to provide a spread illuminating apparatus which can reliably fix each component while ensuring the strength, reducing the entire thickness, and realizing a natural liquid crystal image.
In order to solve the above problems, according to a first aspect of the present invention, in a spread illuminating apparatus in which a light reflection pattern is formed on a top surface of a light conductive plate made of a light-transmissible material, and a lamp comprising a light conductive bar and a spot-like light source disposed on an end of the light conductive bar is disposed along and close to at least one side surface of the light conductive plate, and which is disposed over a top surface of an LCD, a top side portion of the LCD is fitted into a cut-away portion at a center of a frame covering the lamp and a peripheral portion of the light conductive plate, and a space between a bottom surface of the light conductive plate and a top surface of the LCD is set to be small.
In the configuration according to the first aspect, thanks to the frame provided, each member constituting the spread illuminating apparatus can be reliably fixed in place, in particular, the light source can be reliably fixed at a predetermined position with respect to the light conductive bar, and, as a result, light emitted from the light source can be efficiently guided into the light conductive bar. Further, since the space between the bottom surface of the transparent substrate and the top surface of the LCD is reduced by fitting the top side portion of the LCD into the cut-away portion at the center of the frame, the thickness of the entire apparatus, which is conventionally increased by the thickness of the entire frame, can be reduced. In addition, since the thickness of the entire frame need not be reduced, the strength of the frame can be ensured.
In order to solve the above problems, according to a second aspect of the present invention, in a spread illuminating apparatus, in which a light reflection pattern is formed on a top surface of a light conductive plate made of a light-transmissible material, and a lamp comprising a light conductive bar and a spot-like light source disposed on an end of the light conductive bar is disposed along and close to at least one side surface of the light conductive plate, and which is disposed over a top surface of an LCD, a top side portion of the LCD is fitted into a cut away portion at a center of a frame covering the lamp and a peripheral portion of the light conductive plate, and a bottom surface of the light conductive plate is in contact with a top surface of the LCD.
In the configuration according to the second aspect, the top side of the LCD is fitted into the cut-away portion at the center of the frame so that the top surface of the LCD gets into contact with the bottom surface of the light conductive plate, whereby the thickness of the entire apparatus is reduced.